Studies on the Transmission of Simian Malarias, I. Transmission of Two Strains of Plasmodium inui by Anopheles maculatus and A. stephensi

Abstract

Five species of Anopheles mosquitoes were examined in regard to their susceptibility to infection with the OS and L strains of Plasmodium inui. Anopheles maculatus and A. stephensi were readily infected and were able to transmit each of the strains by bite. Three New World mosquitoes, A. quadrirraculatus, A. freeborni, and A. albimanus, became infected. The A. quadrimaculatus rarely exhibited sporozoite-positive salivary glands. The other two species failed to produce gland infections. The malaria parasite, Plasmodium inui, naturally infects monkeys throughout much of South and Southeast Asia. This parasite has a quartan periodicity and has been isolated from Macaca irus, M. mulatta, M. nemestrina, M. radiata, and Cynopithecus niger (see Eyles, 1963, for a discussion of this parasite and its geographical and host distribution). The development of this species to the sporozoite level in mosquitoes has been demonstrated in A. atroparvus (Weyer, 1937; Garnham, 1951; Mohiuddin, 1957; and Shortt et al., 1963), in A. quadrimaculatus (see Eyles, 1960) and in A. stephensi (see Shortt et al., 1963). Garnham (1951) obtained transmission of this species to M. mullatta (rhesus monkey) by the bites of infected A. atroparvus mosquitoes coupled with the intravenous inoculation of dissected salivary glands. Mohiuddin (1957) passaged the parasite to Al. miulatta by the inoculation of dissected glands from infected A. aztecus. He also fed infected A. atroparvus and A. aztecus on a monkey which later developed a patent infection. In this latter instance, it is impossible to say which species of mosquito transmitted the parasite. Eyles (1960) obtained transfer by the intravenous inoculation of dissected salivary glands from infected A. quadrimaculatus. Shortt et al. (1963) transferred P. inui by the intravenous inoculation of salivary glands containing sporozoites from A. aztecus and from A. stephensi. The only transmission by mosquito bite appears to be that reported above by Mohiuddin (1957). A number of strains of P. inui are being investigated in this laboratory. Reported here Received for publication 4 April 1966. 664 are the results of mosquito infection and transmission studies involving two different strains of P. inui malaria and five species of Anopheles mosquitoes. MATERIALS AND METHODS The strains of malaria used were the OS and L strains of P. inui. For information dealing with the origin and designation of the OS strain see Coatney et al. (1966). The L strain of P. inui was isolated from a naturally infected A. leucosphyrus mosquito collected in Malaya by Wharton et al. (1962). This parasite, like the OS strain, was obtained from our laboratory in Malaysia. The A. quadrimaculatus mosquitoes were the Q-1 strain which was obtained from Technical Development Laboratories, CDC, Savannah, Georgia, and maintained in our laboratory since 1959. The A. freeborni (F-1 strain) were from Marysville, California, and have been maintained in the laboratory since 1944. The A. stephensi were from Delhi, India, and were obtained from the London School of Hygiene and Tropical MNedicine, London, England in 1963. The A. albimanus mosquitoes were the A-9 strain originally obtained from San Salvador, and maintained in our laboratory since 1960. The A. maculatus were obtained from the Institute for Medical Research, Kuala Lumpur, Malaysia, in 1964, and have been maintained in our laboratory since then. Monkeys (M. mulatta) were infected by the intravenous inoculation of parasitized blood or by intrahepatic inoculation of sporozoites. When gametocytes were present in the peripheral blood, mosquitoes were allowed to feed. All mosquitoes were insectary reared and after feeding were incubated at a temperature of 78 to 80 F and at high humidity. Mosquitoes were fed 5% Karo syrup daily on a cotton pledget. Dissections to determine presence and number of oocysts on the gut were begun 6 days after feeding. Since transmission was the primary goal of these studies, only a minimum number of mosquito guts were examined (normally five to 11). Salivary gland dissections were made only after This content downloaded from 157.55.39.185 on Thu, 26 May 2016 04:40:27 UTC All use subject to http://about.jstor.org/terms COLLINS ET AL.-TRANSMISSION OF PLASMODIUM INUI BY ANOPHELES SPP. 665 TABLE I. Infection of Anopheles maculatus mosquitoes with the OS strain of Plasmodium inui. Days postGametocytes per inoculation 100 WBC Mosquitoes Per cent Avg no. Monkey (Days of dissected infection oocysts per patency) Male Female pos. gut Blood-induced infections T-163 7 20 44 7 100 38 8 50 60 6 100 46 9 20 260 5 100 37 T-166 8 4 18 8 75 42